<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <canvas id="tutorial" width="300" height="300"></canvas>
  <script>
    function draw() {
      var canvas = document.getElementById('tutorial');
      if (!canvas.getContext) return;
      var ctx = canvas.getContext("2d");

      ctx.beginPath();
      ctx.arc(120, 120, 100, 0, Math.PI * 2);
      ctx.clip();

      ctx.fillStyle = "pink";
      ctx.fillRect(120, 120, 100, 100);
    }
    draw();
  </script>
</body>

</html>